The present invention relates to a control device for a hybrid vehicle powered from an engine and an assist motor for assisting the engine.
A typical hybrid vehicle is usually powered by its engine and, during acceleration, is additionally powered by an assist motor output of which is uniformly predetermined according to current conditions of the vehicle.
Thus, a conventional control means for the hybrid vehicle causes the assist motor to work by supplying always a uniformly determined power to help the engine even when the catalyzer device for cleaning exhaust gas from the engine is not warmed up to a temperature necessary for activating a catalyzer therein.
Furthermore, the hybrid vehicle is provided with control means that usually stops the engine for its idling time to save fuel consumption and restarts the engine when restarting the vehicle.
Consequently, the hybrid vehicle may cut off the idling engine with the catalyzer device being inactive at a low temperature.
The problems involved in the control system of the conventional hybrid vehicle powered by a combination of an engine with an assist motor are such that the control causes the assist motor to help the engine when the catalyzer device for cleaning exhaust gas from the engine is inactive at a low temperature and causes the idling engine to stop with the catalyzer device being in inactive state. In such cases, it requires much time to warm the catalyzer device to the working temperature necessary for cleaning exhaust gas from the engine.
Accordingly, a primary object of the present invention is to provide a control device for a hybrid vehicle, which device controls an assist motor to supply electric power to a main engine when accelerating the vehicle and which includes means for detecting a temperature of a catalyzer device and correcting a predetermined assist power value, when a current temperature of the catalyzer device is lower than a specified temperature so that the catalyzer therein can be rapidly activated by heat.
Another object of the present invention is to provide a control device for a hybrid vehicle powered by a combination of a main engine and an assist motor, which detects a temperature of a catalyzer device and, when the detected temperature of the catalyzer device is lower than a specified value, prohibits the engine to stop idling so as to immediately heat the catalyzer device to the temperature at which catalyzer therein actively work for cleaning the engine exhaust gas.